1. Reservation of Copyright
This patent document contains material subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document, as it appears in the U.S. Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
2. Field of the Invention
The present invention is related to processes for moving data through a disk media access channel and systems and methods for managing such processes.
3. Description of Background Information
Hard disk drives, tape drives, and other movable storage media devices transfer data between an I/O controller and movable storage media through a media access channel (also known as a read channel). The media access channel is the route over which information is transferred for read, write, and compare operations, and couples an I/O controller to the media. The media access channel may comprise, among various elements, a plural pin serial or parallel interface coupling the I/O controller to an actuator driver, a read/write head, and, for media read operations, a signal converter for converting an analog signal to a sequence of bits representative of data on the media. In the case of a Partial Response Maximum Likelihood (PRML) disk drive read channel, the disk drive comprises digital signal processing components and components for performing maximum likelihood detection, to facilitate the fast and accurate transfer of data between the disk I/O controller and the disk media.
Media access channels, such as the PRML read channel, are provided with sophisticated filtering and other digital signal processing mechanisms for improving disk performance, by improving such disk characteristics as areal density (disk capacity), data transfer speed, yield, and disk noise. Such improvements are being achieved by PRML read channels without inter-symbol interference (ISI), which results from the overlapping of analog signal peaks being transferred through the read/write head at very large speeds. Rather than merely detecting signal peaks from the media, PRML read channels detect the analog signal from the read/write head, convert the signal to a digital signal, and use the digital signal to detect data bits.
Because disk drives are moving to the use of PRML read channels, aimed at increasing the capacity of the disk drive without sacrificing performance, the latency of data transferred between the media and the I/O controller has increased substantially. As media access channels increase in their latency, it becomes more difficult for the I/O controller to manage transfers over the media access channel. The controller may need to fetch from the disk certain data required to perform various processes associated with a particular operation. Due to the latency of the media access channel, before the fetch process receives the requested information, a large quantity of other data, for example, 20 bytes or more, will be moved through the access channel. Accordingly, the information to be fetched is requested early, and information required for a next process that needs information for the fetch process will be requested immediately thereafter. In this way, when the fetched data is obtained, the data associated with the next process will be provided to the controller shortly thereafter. These media access operations must be requested ahead of time keeping in mind their position within the pipeline and the time at which they will be carried out. If the media access operations are not properly carried out taking these factors into account, problems can be encountered such as destroying adjacent blocks of information, misreading information from the media, or failing to read requested information from the media. In addition, a dependent process, if not provided with timely information from a process upon which it depends, could experience an error.
Accordingly, there is a need for mechanisms for structuring data transfer processes involving the disk media access channel so the controller can accurately handle timing issues and efficiently perform read, write, and compare operations in a pipeline fashion while minimizing access delays, data transfer delays, and errors associated with such operations. There is a need for a scheme which allows for the accumulation of status information regarding the processes used to carry out such operations.
4. Definitions of Terms
The following term definitions are provided to assist in conveying to the reader an understanding of the descriptions provided in this patent document.
Pipe: A portion of memory which is coupled to the output of one process as well as to the input of another process, and allows the process to pass information along to the other process.
Pipeline: A structure comprising multiple sequential stages through which a computation flows as time progresses, wherein at any given time a new operation may be initiated at a starting stage (the start of the pipeline) while one or more other (earlier initiated) operations are in progress and thus at later stages (in the middlexe2x80x94moving toward the end) of the pipeline).
Pour: To send a file or output from a program to another file or to a device using a pipe.
The present invention is provided to improve upon storage subsystems. More specifically, the present invention may be provided to improve upon interfacing subsystems for interfacing a storage media controller to a media access channel which couples the storage media controller to a read/write assembly for writing information to and reading information from the storage media. More specifically, the present invention may improve upon read channel interfacing subsystems which interface a disk controller to the read channel which couples the disk controller to a head disk assembly. In order to achieve these objects, one or more aspects of the present invention may be followed in order to bring about one or more specific objects and advantages, such as those noted below.
The present invention, therefore, is directed to a system or method, or one or more components thereof, involving a non-volatile storage subsystem comprising a media I/O controller, a media access channel, and movable storage media. More specifically, the present invention is directed to a non-volatile disk storage subsystem having a read channel coupling a disk controller to a disk head assembly. A read channel interfacing subsystem is provided as part of the storage subsystem, and the read channel interfacing subsystem interfaces a disk controller to the read channel. The read channel interfacing subsystem comprises a set of process units and a pipeline manager. The set of process units includes first, second and third subsets. The first subset is utilized when a disk read operation is carried out via the read channel. The second subset is utilized when a disk write operation is carried out via the read channel. The third subset is utilized when a disk compare operation is carried out via the read channel. Each process unit comprises mechanisms for entering an idle state and for carrying out an operational state flow. The pipeline manager, for each one of the disk read, disk write and disk compare operations, enables and disables each utilized process unit, so each of the utilized process units is done and ready to carry out its operational state flow for a subsequent operation and has poured into a holding register resulting data needed by a dependent process unit within the present operation, all before the occurrence of a predetermined upcoming periodically recurring advance signal.